SH-SY5Y and Poly-L-Lysine

Hello everybody,
I am having problem with neuroblastoma cell line, in particular when I seed the cells on the petri dish, most of them remain in suspension.
Looking on line I see that to overcome this problem some people use poly-l-lysine but I have no idea how to use it,
furthermore, sigma has many type of poly-lysine, could please someone tell me how to use it ? and which kind of poly-lysine is good in term of molecular weight ?

as you can see in this image, after 24 hours most of the cells are attached, but they appear spherical and weird, maybe there is some step that needs to be modified or anyway I don't know ...if you guys have any suggestions could be useful for me and for somebody else in the future